Recent electric vehicles and hybrid vehicles employ a storage battery serving as an electric power supply unit for an electric motor, which is a drive source for such vehicles. As a system for recharging such a storage battery, a charging system having a charging device for supplying electric power to the storage battery, such as a charging station, has been proposed. Specifically, to recharge the storage battery using the system, a feeding plug, which is attached to a distal end of an electric power supply cable extending from the charging device, is inserted into a feeding port formed in the vehicle. This electrically connects the feeding plug to the storage battery in the vehicle. The storage battery is thus recharged by supplying electric power from the charging device to the storage battery through the electric power supply cable.
In contrast, a non-contact charging system has been proposed as a system for supplying electric power from a charging device to a storage battery without using the aforementioned electric power supply cable. Referring to FIG. 10, as described in Patent Document 1, for example, the non-contact charging system includes a charging device having an electric power transmission coil 1, which is embedded in the ground surface in advance. An electric power reception coil 2 is mounted in a lower body portion of a vehicle, which is a charging target. The electric power reception coil 2 is positioned to face the electric power transmission coil 1 to cause electric power transmission from the electric power transmission coil 1 to the electric power reception coil 2 through mutual induction or resonance brought about by electromagnetic coupling between the electric power transmission coil 1 and the electric power reception coil 2. Also, to control the electric power transmitted from the charging device to the storage battery, the non-contact charging system performs wireless communication between a charging-side wireless communication device, which is installed in the charging device, and an in-vehicle wireless communication device, which is mounted in the vehicle. However, when the wireless communication is carried out between the two wireless communication devices at a position close to the electric power transmission coil 1 and the electric power reception coil 2, the communication is influenced to a measurable extent by noise caused by a magnetic field produced between the electric power transmission coil 1 and the electric power reception coil 2. To solve this problem, typically in such non-contact charging systems, the two wireless communication devices are arranged at such positions that the wireless communication devices are prevented from being influenced by the magnetic field between the coils 1, 2, thus performing remote communication. To carry out wireless communication, pairing is carried out to ensure that the vehicle having the storage battery that is the charging target for the charging device corresponds to the vehicle that is the target for the wireless communication.
In the above-described charging system, the charging device may be used by an indefinite number of vehicles for recharging. In this case, an electric power transmission coil is embedded in each of a plurality of charging areas and the vehicles, which are the charging targets, are arranged in the respective charging areas. Also in this case, remote communication is carried out between the charging device and each of the vehicles. However, the charging device receives multiple wireless signals from the vehicles, which are, specifically, the corresponding in-vehicle wireless communication devices of the vehicles. This decreases accuracy in the aforementioned pairing.
To solve this problem, as described in Patent Document 2, a non-contact charging system has an electric power transmission device, which obtains identification information (ID information) from a portable device (a device to be recharged) as a charging target. Based on the obtained ID, the electric power transmission device authenticates the portable device as the charging target. Referring to FIG. 11, this non-contact charging system includes a plurality of electric power feeding devices 12, which have near field communication function and non-contact charging function for a portable device 20. Each of the electric power feeding devices 12 detects electromagnetic waves transmitted from the portable device 20, which is carried by the user, as an ID signal specific to the portable device 20. The electric power feeding device 12 then provides intensity information of the detected electromagnetic wave to a server device 16. The server device 16 has database storing IDs of different portable devices 20, which have been registered in advance. Specifically, based on a set of intensity information regarding the ID signals received by the electric power feeding devices 12, the server device 16 identifies the electric power feeding device 12 that corresponds to the most intense electromagnetic wave as the electric power feeding point for recharging the portable device 20. Subsequently, for the identified electric power feeding device 12, a monitor 14 serving as a display device arranged in parallel with the electric power feeding device 12 displays that the electric power feeding device 12 is now capable of charging. Then, based on comparison between the ID of the portable device 20 obtained by the identified electric power feeding device 12 and the corresponding ID registered in the database, the server device 16 authenticates the portable device 20 and sets a charging condition for the portable device 20 through the identified electric power feeding device 12. In this manner, the electric power feeding device 12 is caused to perform non-contact charging on the portable device 20.